Electric Turbocharger Reverse Rotation for Catalyst Warm-Up
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Solution Overview
Problem
Existing electric turbocharger systems are inefficient in quickly warming up the catalyst during a cold start, as exhaust flow typically goes through the turbine, leading to heat loss rather than being effectively utilized for catalyst heating.
Innovation Solution
A control system that directs exhaust flow through a wastegate instead of the turbine, using a wastegate valve and controller to manage the electric turbocharger's speed and direction, ensuring no flow through the turbine during cold starts to maximize heat flux to the catalyst, and switching to normal operation once the catalyst reaches a satisfactory temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If exhaust flow is directed through the turbine of the electric turbocharger, then the turbine is driven to produce compression, but heat is lost through the turbocharger housing that could otherwise be used to heat the catalyst
Solution Approach 1:
The patent inverts the normal exhaust flow direction by commanding the electric turbocharger to rotate in reverse direction. This reversal blocks the exhaust path through the turbine and redirects it through the wastegate system, preventing heat loss through the turbocharger housing and directing heat to the catalyst for faster warm-up.
Solution Approach 2:
The wastegate system serves as an intermediary component that redirects exhaust flow. By opening the wastegate valve and reversing turbocharger rotation, the exhaust is routed through the wastegate passage instead of the turbine, allowing heat to be directed to the catalyst while still maintaining the ability to control exhaust flow.
2Temperature
If the electric turbocharger rotates in reverse direction to block exhaust flow through the turbine, then heat flux to the catalyst increases, but the system complexity increases due to reverse rotation control
Solution Approach 1:
The electric turbocharger is designed with multi-functionality, capable of operating in both forward and reverse directions. This universal rotation capability allows the same component to serve dual purposes: normal forward rotation for compression and reverse rotation for blocking exhaust flow and directing it through the wastegate, eliminating the need for additional mechanical components.
Solution Approach 2:
The patent replaces traditional mechanical exhaust flow control mechanisms with an electrically controlled system. The electric motor controlling the turbocharger can be commanded to rotate in reverse through electronic control, substituting complex mechanical flow diversion mechanisms with simpler electrical control of the existing electric turbocharger.
3Loss of time
If exhaust flow is redirected through the wastegate to heat the catalyst, then warm-up time is reduced, but the turbocharger cannot simultaneously perform compression function
Solution Approach 1:
The system employs periodic action by alternating between reverse rotation mode (for catalyst warm-up) and forward rotation mode (for normal compression). During cold start conditions, the turbocharger operates in reverse to heat the catalyst. Once the catalyst reaches operating temperature, the system switches to forward rotation to restore normal compression function, creating a time-based operational sequence that satisfies both requirements.
Solution Approach 2:
The system performs preliminary action by using reverse rotation of the turbocharger before normal operation to pre-heat the catalyst. This preliminary heating phase occurs during cold start conditions, preparing the catalyst for efficient operation before the engine transitions to normal forward-rotation compression mode.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces warm-up time of the catalyst by redirecting exhaust flow through the wastegate, minimizing heat loss and efficiently utilizing exhaust heat for catalyst heating, thereby improving emissions reduction during cold starts.
Implementation Method 1
commanding the electric turbocharger to rotate in a reverse direction at a desired reverse speed to satisfy no flow of the exhaust gas through the turbine
Implementation Method 2
direct exhaust flow through a wastegate, rather than a turbine of the turbocharger, to increase heat flux in a catalyst to reduce warm up time during a cold start
Implementation Method 3
obtain a set of parameters including an exhaust flow rate through the exhaust system
Data Source
AI summary
A control system for an engine comprising an electric turbocharger and a wastegate is presented. The system is configured to variably open and close to control the flow of exhaust gas in an exhaust system of the engine at a turbine of the electric turbocharger; and a controller that obtains parameters including an exhaust flow rate through the exhaust system. The controller uses the parameters to (i) determine a desired speed of the electric turbocharger to satisfy no flow of the exhaust gas through the turbine; (ii) command the electric turbocharger to rotate in a reverse direction at the desired speed to achieve no flow of the exhaust gas through the turbine; (iii) determine whether an exhaust gas treatment system (ETS) has reached a desired temperature; and (iv) command the electric turbocharger to rotate in a forward direction based on the ETS reaching the desired temperature.